Pulling Double/Triple Trailers: Tracking, Off-Tracking, and Turns
Tracking, Off-Tracking, and Turns
This domain tests how a multi-trailer combination follows a curve. Off-tracking is the difference between the path of the front wheels and the path of the rear wheels. Each articulation adds off-tracking, so the last trailer of a double or triple cuts the corner more sharply than a single semi-trailer. Rearward amplification means a small steer input at the tractor can produce a large lateral move at the rear trailer.
Core rules
- Start turns from the proper lane; do not swing wide into oncoming traffic without checking mirrors.
- Delay the turn until the tractor clears the curb line, then follow the trailer's track through the mirrors.
- Watch the rear trailer's tires, not the trailer body, to judge clearance.
- Keep speed low in turns; a multi-trailer combination can roll over at lower speeds than a single.
- Use both mirrors and a spotter when available for tight right turns.
Worked example
A driver making a right turn at a city corner starts the turn when the tractor cab reaches the crosswalk. The first trailer tracks inside the curb, and the second trailer's left rear tires strike the curb because the driver did not allow for added off-tracking. Correct technique: pull forward until the tractor is past the corner, then turn slowly while watching the last trailer's wheels in the right mirror.
Traps
- Turning too early; this is the most common cause of curb strikes and pole hits.
- Watching the trailer body instead of the tires.
- Assuming a dolly behaves like a fixed axle; it pivots and changes the tracking path.
- Forgetting tail swing at the front of the first trailer when leaving a tight dock.